Revision as of 21:20, 18 August 2012

This is a comprehensive timeline of monad tutorials and related articles.

Please update this list as it becomes outdated! If you find a tutorial, article, post, comment, or message that stands on its own as an explanation of monads, then please take a moment to paste the link somewhere on this page (register a throwaway account, if you prefer). The date, author, and blurb can be added later. This will greatly help others who are using this list as a resource for learning about monads.

"Once upon a time, people wrote their Haskell programs by sequencing together operations in an ad-hoc way." ... "For our purposes, a monad is a triple of a type and then> & return operators defined over it so that the following laws apply: ..."

"Writing introductions to monads seems to have developed into an industry," Dan (sigfpe) observes. He argues that monads are not "something esoteric in need of explanation", but walks you through the process of reinventing monads to solve some very basic and practical problems.

Monad transformers are rarely covered in introductory tutorials. This "is not a paper about implementing transformers, but about using them to write elegant, clean and powerful programs in Haskell". Available as a 12 page PDF or .lhs file.

Author's Description: This crash course starts with an EASY! introduction to categories and functors, then we define a monad, then give some basic examples of monads in categories, then present monadic terminology as used in programming languages.

Csgordon reports that monad tutorials tend to "get horribly botched" and says "[they] either bored me to tears, struck me as completely inane, or simply confused me". He uncovers the early Phil Wadler's paper, Monads for Functional Programming, which not only gives a clear explanation but provides non-trivial motivating examples

10 year 2010

An example showing how a simple Java class is translated into a stack of monad transformers, with a metaphor about how monads are like conversations, and why this idea should be familiar to OO programmers.

11 year 2011

"Monads are hard to describe because they don’t correspond to anything in our everyday experience" ... "A monad is an endofunctor together with two special families of morphisms, both going vertically, one up and one down"